DE102013107012B4 - Method for operating a battery converter and bidirectional battery converter - Google Patents

Abstract

A method of operating a bidirectional battery converter (11) connected to an AC mains (13) taking into account the availability of locally generated electrical power, comprising: - defining a plurality of operating modes (1, 3, 4, 5, 10, 20) of the battery converter (11) supplying electric power to an input side battery (14) and outputting electric power from the battery (14) in response to a state of charge of the battery (14) and electric power available on the output side; - Defining multiple thresholds (A to G) for the state of charge of the battery (14); and - falling below a first lower threshold (F), switching from a first mode of operation (1) in which electrical power is output from the battery (14) when a local power requirement is not covered by the locally generated electrical power and / or there is a global underpower of electrical power in the AC grid (13), and in which electrical power is fed to the battery (14) when the locally generated electrical power exceeds the local power demand and / or if there is a global oversupply of electrical power in the battery AC mains (13) is present, in a second operating mode (3), characterized in that - in the second operating mode (3) no electric power from the battery (14) or only electric power from the battery (14) is output, if the local power requirement is not covered at all, and electric power is fed into the battery (14) when lo cal electric power generated is available and / or when there is a global oversupply of electrical power in the AC mains (13), that at a state of charge (SOC) below a second lower threshold (D) which is below the first lower threshold (F) if, on the output side, electrical power is available, the battery (14) is charged by supplying electrical power until reaching a first upper threshold (E) that is less than or equal to the first lower threshold (F), wherein a first difference ( Grid Res) between the first upper threshold (E) and the second lower threshold (D) is selected so that a standby consumption of the battery converter (11) is covered for a predetermined first period.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a method for operating a bi-directional battery converter connected to an AC network, taking into account the availability of locally generated electrical power, comprising the steps of the preamble of independent claim 1.

Furthermore, the present invention relates to a battery converter with measuring devices for detecting the state of charge of a connected battery and with a controller that performs the method.

In particular, the battery converter may be a DC / AC converter connected directly to the AC mains or to a stand alone network normally connected to the AC mains. Such a battery converter is also referred to as a battery inverter.

If the battery converter according to the invention is designed as a battery inverter, it may be designed as an island inverter, which is able to specify an AC voltage in the island grid when the island grid, for. B. at the collapse of the AC network, has separated from this. This mode of operation of the battery converter is called in the following replacement power operation.

The battery converter can furthermore be a DC / DC converter which is connected to a DC intermediate circuit of a DC / AC converter, which is connected on the output side to the AC mains or to a stand-alone network normally connected to the AC mains. In this case, at least one further current source can be connected to the DC voltage intermediate circuit of the DC / AC converter, such as a photovoltaic generator.

In general, locally generated electrical energy whose availability is taken into account in the operation of the battery converter is preferably generated from a regenerative primary energy and in particular with a photovoltaic generator.

If this is an "AC network" is mentioned, it is such, in which the AC voltage is set by a device other than the invention operated or even inventive inverter. It can be a local or national, public or private AC network.

If this is referred to as "a battery" connected to the battery converter, this may be a single battery unit. The battery can also have a plurality of parallel and / or serially connected units. In particular, it will regularly have a plurality of individual cells.

When this specification and claims refer to "lower" thresholds and "falling below" lower thresholds, these formulations are intended to indicate that a particular action should be taken when a reading is from a value above the threshold to a lower threshold Value falls below the threshold value. An upper threshold value is accordingly a threshold value at which an action is to take place when a measured value rises from a value below the threshold value to a value above the threshold value. In this case, the respective action can already be triggered when the changing value of the respective measured value is equal to the lower or upper measured value. However, it is often easier to determine whether the measured value falls below the respective lower threshold value or exceeds the respective upper threshold value.

In the present description and claims, when a "first", "second", "third" etc. threshold or mode of operation or period or a "first", "second", etc., difference is mentioned, it is not intended to give any order of merit or sequence. Rather, these statements are only intended to facilitate reference to the respective thresholds, operating modes, periods and differences.

STATE OF THE ART

From the EP 1 965 483 A1 An auxiliary device is known which is to be arranged between a public alternating current network and a self-generating installation. The additional device has an independent release point, with which the self-generating system can be connected to the AC mains. A network monitoring device located in the additional device opens the independent disconnection point in the event of a power failure of the public AC network. About a second switching element of the auxiliary device, the self-generating system is an island grid with several connected to the additional equipment consumers and an island inverter switched on. The island inverter is powered by a battery. A switch is also the island network normally connected to the public power grid, so that this specifies an AC voltage in the island grid. Only if the AC mains fails, the island grid is disconnected from the AC mains. Then the island inverter specifies the AC voltage in the island grid. On this AC voltage, the self-generating system with the second Switching element can be switched. If the stand-alone grid is connected to and supplied from the public AC grid, the battery of the stand-alone inverter is constantly recharged, so that enough energy is available in the event of a failure of the AC grid. In this case, the energy flow and the voltage of the battery can be influenced so that a long life of the battery is ensured.

From the final report "Modular battery power converter: Development of a battery converter for the modular system technology in PV systems", funded by the Federal Ministry of Education, Science, Research and Technology, license plate number: 0329741, a control of an island inverter depending on the state of charge of its battery is known. The state of charge is divided into three work areas "battery normal", "battery low" and "battery overloaded". The work area "battery normal" comprises subareas "N" with a charge state between 60% and 100%, "V1" with a charge state between 40% and 60% and "V2" with a charge state between 20% and 40%. In the region V2 of low availability of the battery, a diesel generator for charging the battery is started, if it is present in the island grid. The work area "battery low" is divided into a subarea "A1" with a charge state of 10% to 20%, a subarea "A2" with a charge state of 0% to 10% and a subarea "A3" with a charge state below 0% , In subarea A1, the consumers in the off-grid are partially switched off. In subarea A2, all consumers in the off-grid are switched off. In the subarea A3 and the island inverter is turned off to prevent a deep discharge of the battery. The work area "battery overloaded" is subdivided into two sections "UE1" and "UE2" with increasing overcharging of the battery. In the first subarea UE1, additional switchable loads are switched on. If the battery voltage continues to increase up to the range UE2, current feeders connected to the stand-alone grid, such as photovoltaic and wind power plants, are switched off or switched off.

Batteries are also used as a buffer for electrical energy derived from regenerative primary energies to increase local self-consumption of that electrical energy at the point of its generation. In this case, electrical power is supplied via a battery converter of the respective battery as long as it can absorb electrical power, if there is an excess of locally generated electrical power compared to the local power requirement. Conversely, the battery is taken as long as electrical power, as they can provide these, if the locally generated electrical power does not meet the local power requirements. In order to prevent a further deep discharge of the battery, the battery is kept at a minimum state of charge. Occurring self-discharge of the battery is compensated by supplying electrical power, which is taken if necessary, a connected AC mains.

OBJECT OF THE INVENTION

The invention has for its object to provide a method for operating bidirectional battery converter, taking into account the availability of locally generated electrical power, which ensures maximum functionality of the battery converter with maximum efficiency and minimum load on the battery. In addition, a corresponding battery converter will be shown.

SOLUTION

The object of the invention is achieved by a method having the features of the independent patent claim 1 and by a battery converter having the features of claim 17. The dependent claims define preferred embodiments of the method and the battery converter according to the invention.

DESCRIPTION OF THE INVENTION

The invention provides a method for operating a bidirectional battery converter taking into account the availability of locally generated electrical power. At the beginning of the method, several operating modes of the battery converter are defined in terms of when feeding electrical power into a battery connected on the input side or outputting electrical power from the battery as a function of a charging state of the battery and of electrical power available on the output side. For this purpose, several thresholds for the state of charge of the battery are defined. When falling below a first lower threshold value is changed from a first operating mode in a second operating mode. In the first mode of operation, electrical power is output from the battery when a local power demand is not met by the locally generated electrical power and / or when there is a global under-supply of electric power in the AC power grid. Electrical power is fed into the battery in the first operating mode when the locally generated electrical power exceeds the local power requirement and / or when there is a global over-supply of electrical power in the AC power grid. In the second mode of operation, electrical power from the battery is output at most when the local power requirement is not covered at all. Electrical power is fed into the battery in the second mode of operation when locally generated electrical power is available and / or when there is a global over-supply of electrical power. In a state of charge below a second lower threshold, which is below the first lower threshold, the battery is charged by supplying electrical power until reaching a first upper threshold that is less than or equal to the first lower threshold. This charging takes place, if at the output electric power is available at all. The first upper threshold is defined relative to the second lower threshold such that a first difference between the first upper threshold and the second lower threshold covers a standby consumption of the battery converter for a predetermined first period of time.

A "global underpower of electrical power" is understood to mean a situation in which the demand for electrical power across the AC network has to be adapted to a limited supply of electrical power. In such a situation, all loads connected to the AC network become basically still sufficiently supplied; Nevertheless, a support of the AC network by feeding additional electrical energy makes sense.

When the statement of "and / or" is made in the definition of the present invention, it is meant that the conditions associated therewith may be set individually or jointly, and in the latter case, it suffices that one of both conditions is satisfied to trigger the dependent action. Thus, in the first mode of operation, electrical power may be output from the battery when a local power requirement is not met by locally generated electrical power, without regard for a global under-supply of electrical power. Likewise, in the first mode of operation, only when there is a global underpower of electrical power, can electrical power be output from the battery without regard to a relationship between the local power demand and the locally generated electrical power. Finally, in the first mode of operation, electrical power may be output from the battery both when the local power requirement is not met by locally generated electrical power and when there is a global under-supply of electrical power. The same applies to the other conditions linked by the indication "and / or".

Regardless of the explanation in the last paragraph, it is preferred for the second mode of operation that electrical power be fed into the battery both when locally generated electrical power is available and when there is a global over-supply of electrical power.

In either case, when switching from the first mode of operation to the second mode of operation, the output of electrical power from the battery is severely limited, either to zero or, if the battery is also intended for backup power, to those situations where the local power requirement is at all is not covered, because the AC network is overloaded or collapsed. In addition, the supply of electrical power to the battery is extended to situations in which locally generated electrical power is available. Thus, in the second mode of operation, on the one hand, further discharge of the battery is prevented as far as possible. On the other hand, as far as possible recharging the battery takes place by supplying locally generated electrical power, so that the battery is again available as an active buffer for locally generated electrical power and / or the global supply of electrical power.

If the state of charge of the battery continues to fall below the second lower threshold, which is below the first lower threshold, the battery, if any electrical power at the output of the battery converter is available, recharged until its state of charge reaches a first upper threshold. The amount of electrical energy fed into the battery is adjusted so that it covers a standby consumption of the battery converter for a predetermined first period of time. Even if subsequently no further power is fed into the battery, because no locally generated electrical power is available, the state of charge of the battery will reach the second lower threshold only after the predetermined first period again. This period can z. B. be set to a value ≥ 12 hours in order to wait with a photovoltaic generator locally generated electrical power overnight, whether not the next morning locally produced electrical power is available again. The first difference between the first upper threshold to which the battery is charged in doubt with electrical power from the AC mains, and the second lower threshold is also to be chosen at least so large that operation of the battery converter when charging the battery until reaching the first upper threshold with an optimized, ie maximum efficiency is possible. Such efficiency is usually only at a comparatively large Charging current to the battery reached over a minimum period. In any case, the present invention does not pursue the concept of minimizing the first difference between the first upper threshold and the second lower threshold in order to remove as little electrical energy as possible from the AC grid during a charging process. Rather, the electrical energy taken from the alternating current network is used as efficiently as possible, and it is equal to so much electrical energy fed from the AC mains in the battery that with reasonable probability no further such feed must be made because within the first period, the locally generated electrical power is available again.

If, in the method according to the invention, a third lower threshold, which lies below the second lower threshold value, is undershot, it is possible to switch from the second operating mode to a third operating mode, in which electrical power from the battery only covers the standby consumption of the battery converter is used and in the electrical power is fed into the battery when electrical output is available on the output side. That is, falling below the third lower threshold will stop any output of electrical energy from the battery to the outside. The energy consumption is thus limited to that of the battery converter. Thus, the remaining residual charge of the battery can be used over a maximum period of time to maintain the operational readiness of the battery converter. Once electrical output is available on the output side, the battery is recharged. This requires no restart of the battery converter, which is in the third operating mode in a standby mode.

A second difference between the second lower threshold and the third lower threshold, which together limit the portion of the second mode of operation in which no electrical power is available on the output side, may cover an amount of energy that is reserved for backup operation in the second mode of operation. This means that the battery is still sufficiently charged even when the second lower threshold value is reached in order to allow the battery converter and the devices connected to it to operate in the standby mode until the third lower threshold value has been reached.

As soon as a fourth lower threshold value, which is below the third lower threshold value in the case of the provision of the battery for an emergency power operation, is undershot, the battery converter is preferably switched off in the method according to the invention. If no backup power operation is provided by the battery, even in the second operating mode electrical power from the battery is only used to cover the standby consumption of the battery converter. Then, at the bottom, the lower threshold value is directly followed by the fourth lower threshold, below which the battery converter is switched off.

A difference between the directly above the fourth lower threshold, d. H. the lowest above the fourth lower threshold, lying lower threshold and the fourth lower threshold is preferably selected so that the standby consumption of the battery converter is also covered without supply of electrical power into the battery for a predetermined second period. This second period in which the battery converter is in the above-mentioned standby mode and thus allows a recharging of the battery when returning output-side power without manual restart can, for. To 72 hours, or generally to a period in which a return of a broken AC network can be expected. Typically, the second period is many times longer than the first period.

In the method according to the invention, a fourth difference between the fourth lower threshold and a fifth lower threshold, to which at least one manual restart of the battery converter is still possible, may cover the self-discharge of the battery for a predetermined third period of time. Since falling below the fourth threshold, the battery converter is already switched off, no active measures when falling below the fifth lower threshold are no longer possible. Rather, its falling below means that a restart of the battery converter to recharge the battery is no longer readily possible. Accordingly, this fifth threshold should as far as possible never be fallen short of. For this reason, the fourth lower threshold value must be set so far above the fifth lower threshold value that it is also possible to bridge a prolonged failure of the AC network and a simultaneous prolonged failure of the locally generated power. However, with low self-discharge, a residual charge of the battery of a few percentage points is sufficient to cover a comparatively long third period of weeks or even months in this manner. Practically, this value z. For example, it can be set to 3% SOC (State of Charge) as a measure of the state of charge of the battery.

In the method according to the invention, further threshold values may be above the first lower threshold value, such as For example, a sixth lower threshold below which a fourth mode of operation in which electrical power is output from the battery when the local power demand is not covered by locally generated electrical power and when there is a global underpower of electric power, and in the electrical Power is fed into the battery when the locally generated electrical power exceeds the local power requirement and when there is a global oversupply of electrical power, is switched to the first mode of operation. In this case, in the first mode of operation, electric power is output from the battery when there is a global shortage of electric power, and electric power is supplied to the battery when the locally generated electric power exceeds the local power demand and when there is a global oversupply of electric power Performance is present. In this embodiment of the method according to the invention, in the fourth operating mode with the battery, the self-consumption of the locally generated electrical power is also maximized, while in the first operating mode only one network service is provided by providing positive control power for the AC network.

A fifth difference between the sixth lower threshold and the first lower threshold thus provides a certain average positive control power for a given fourth period of time. It is understood that switching between the fourth operating mode and the first operating mode is only possible if such a positive control power is made available to the battery converter and, accordingly, the charging states between the sixth lower threshold and the first lower threshold are reserved for this positive control power ,

When falling below a seventh lower threshold that is above the sixth lower threshold, a fifth operating mode in which electrical power is output from the battery when a local power requirement is not covered by locally generated electrical power and / or a global under-supply is present in electrical power, and in which electrical power is fed into the battery when there is a global overabundance of electrical power, is switched to the fourth operating mode, thereby also a range of charge states above the sixth lower threshold for the provision of control power for the AC mains reserved, in this case of negative control power.

Specifically, a difference between a maximum charge of the battery, with a maximum regular, d. H. the integrity of the battery is not in question charging, and the seventh lower threshold to cover a certain average negative control power for a predetermined fifth period.

In a further development of the method according to the invention, at least one of the threshold values is changed seasonally. Specifically, it is lowered to the summer and raised again after the summer. This takes into account the likely short-term re-availability of local electric power generated by photovoltaic generators in the summer. The concrete course of the seasonally altered lower thresholds may be cosinusoidal, with one year corresponding to one period of the cosine function. It is understood that this information corresponds to the northern hemisphere in relation to one calendar year. In the southern hemisphere, where summer is around the turn of the year, the course of the seasonally altered thresholds shows a negative cosine shape. Due to the threshold values lowered in the summer, a larger spectrum of charging states is available for the normal operation of the battery converter, in which it is available as a buffer for the locally generated electrical power.

In the method according to the invention, furthermore, at least one of the threshold values can be determined as a function of weather forecasts. Thus, for example, in sunny weather the differences between the threshold values can be reduced, because more quickly locally generated electrical power will be available than in the case of heavy cloud cover. At least, this applies to local generation of electrical power by means of photovoltaic generators.

In the method according to the invention, the respective lower threshold values, below which two modes of operation are changed, are typically each assigned an upper threshold value which is greater than or equal to the lower threshold value and, if exceeded, is changed in the reverse direction between the same operating modes. In this case, the respective upper threshold value can be at least slightly above the associated lower threshold value in order to detect unstable states of the battery converter with respect to its operating state, ie. H. a quick and repeated switching between its modes of operation, to avoid.

A battery converter according to the invention has measuring devices for detecting the state of charge of a connected battery and a controller which carries out the method according to the invention. The various thresholds used in the method of the invention may be externally input to the controller be entered. However, the control can also set these threshold values on the basis of external inputs and / or own measured values with respect to the battery connected on the input side and the output-side parameters themselves.

Specifically, the battery converter can be a DC / AC converter for direct connection to an AC mains or an island network connectable to an AC network or a DC / DC converter for connection to an input DC voltage intermediate circuit of a DC / AC converter connected on the output side to an AC network. In the latter case, the DC voltage intermediate circuit is provided for connecting at least one further current source in parallel with the battery converter.

Advantageous developments of the invention will become apparent from the claims, the description and the drawings. The advantages of features and of combinations of several features mentioned in the description are merely exemplary and can take effect alternatively or cumulatively, without the advantages having to be achieved by embodiments according to the invention. Without altering the subject matter of the appended claims, as regards the disclosure of the original application documents and the patent, the following applies: Further features can be found in the drawings. The combination of features of different embodiments of the invention or of features of different claims is also possible deviating from the chosen relationships of the claims and is hereby stimulated. This also applies to those features which are shown in separate drawings or are mentioned in their description. These features can also be combined with features of different claims. Likewise, in the claims listed features for further embodiments of the invention can be omitted.

The features mentioned in the patent claims and the description are to be understood in terms of their number that exactly this number or a greater number than the said number is present, without requiring an explicit use of the adverb "at least". For example, when talking about an element, it should be understood that there is exactly one element, two elements or more elements. These features may be supplemented by other features or be the only characteristics that make up the product in question.

The reference numerals contained in the claims do not limit the scope of the objects protected by the claims. They are for the sole purpose of making the claims easier to understand.

BRIEF DESCRIPTION OF THE FIGURES

The invention is explained in more detail below with reference to embodiments with reference to the accompanying drawings and described.

1 shows an environment in which a method according to the invention and a battery converter according to the invention can be used.

2 shows a different environment in which a method according to the invention and a battery converter according to the invention can be used.

3 is a plot of a state of charge (SOC) as a measure of the state of charge of a battery together with thresholds at which a first embodiment of the method according to the invention between different operating modes of a battery connected to the battery converter is changed.

4 is a 3 corresponding application for a battery converter, in contrast to the battery inverter whose operating modes in 3 are not intended for a backup power operation.

5 is a 3 corresponding application for a battery converter, the opposite of the battery converter whose operating modes in 3 are applied, in addition to the provision of positive and negative control power for an output side connected AC network is formed.

6 is a basically 3 corresponding plot of the SOC of the battery and the associated modes of operation of the battery converter, where the plot is made over a period of one year during which one of the thresholds between two modes of operation changes seasonally.

7 is a 6 corresponding application, whereby here three thresholds change seasonally over the year.

8th is a decision tree that checks the application of the thresholds according to 3 . 6 or 7 illustrated in the corresponding embodiments of the method according to the invention; and

9 FIG. 10 is a network diagram of the various operating modes of the battery converter in the embodiment of the invention according to FIGS 3 and 6 to 8th ,

DESCRIPTION OF THE FIGURES

1 illustrates very schematically the output side connection of a designed as a DC / AC converter bidirectional battery converter 11 over a separation point 12 to an AC mains 13 , On the input side is a battery 14 to the battery converter 11 connected. Before the separation point 12 are loads 15 with the battery converter 11 connected. In case of failure of the AC mains 13 and then opened separation point 12 can the battery converter 11 As an inverters an alternating voltage in one up to the separation point 12 reaching island network 16 form. An inverter 17 with a photovoltaic generator connected on the input side 18 provides locally generated electrical power. About a separation point 19 is the inverter 17 with the net 13 connectable, and via a switchboard 9 with the island grid 16 , In case of failure of the AC mains 13 the inverter disconnects 17 from the AC mains 13 , and then he can after synchronization with that of the battery converter 11 provided AC voltage the island grid 16 over the switching point 9 be switched on. The battery converter 11 is also provided to the battery as a buffer for locally generated electrical power from the photovoltaic generator 18 to maximize self-consumption of this power at the point of its generation. The battery converter 11 has not separately shown measuring devices for detecting a state of charge of the battery 14 in the form of their so-called State of Charge (SOC) and a control device, the current operating mode depending on the detected state of charge and the availability of locally generated electrical power from the photovoltaic generator 18 sets.

2 shows that the battery converter 11 can also be designed as a DC / DC converter, which is connected to an input-side DC voltage intermediate circuit 21 a DC / AC converter 22 is connected, which output side to the AC mains 13 connected. To the DC voltage intermediate circuit is parallel to the battery converter 11 a photovoltaic generator 18 connected as another power source. Dashed lines are an optional DC / DC converter 23 for voltage adjustment indicated by the photovoltaic generator 18 can be connected to the DC voltage intermediate circuit. Even if the battery converter 11 here outputs a direct current, he basically has the same functions as the battery converter 11 according to 1 except that the battery converter 11 according to 2 can not form an AC voltage in a stand-alone grid. But this is the DC / AC converter 22 according to 2 able, even if in 2 none of the AC mains 13 separable island grid is shown.

In the following, various embodiments of an inventive operation of the battery converter 11 according to 1 or 2 depending on the state of charge of its battery connected on the input side 14 and the availability of locally generated electrical power from the photovoltaic generator 18 described.

In 3 the state of charge in the form of the SOC of its battery is applied from 0% to 100%. Certain SOC values are marked as thresholds A, B, C, D, E, F. The differences between these thresholds as well as their distances to the SOC of 100% are not drawn to scale. Rather, here only the sequence of the threshold values A to F is reproduced correctly.

The thresholds B to F are used to indicate the operating mode of the battery converter 11 according to 1 set. The operating mode determines when electrical power from the battery 14 output or vice versa electrical power in the battery 14 is fed. In a region of the SOC above the threshold value F, which is also referred to here as the first lower threshold, and up to a SOC of 100%, the battery converter uses the connected battery in order to maximize self-consumption of locally generated electrical power. In particular, this electrical power is from a regenerative primary energy source and more particularly from the photovoltaic generator 18 according to 1 generated. In addition, at the output of the battery converter is also still electrical power from the AC mains 13 according to 1 to disposal. This electrical power can also be supplied by the battery converter 11 basically in the battery 14 be fed. The operating mode with the main goal of maximizing self-consumption is also referred to as "self" in this description. Since he according to 3 is practiced above the first lower threshold F, it is also the mode of operation which may be meant in this specification and the claims to the "first mode of operation". As this first mode of operation it is in 3 with the reference number 1 Mistake.

When the SOC falls below the first lower threshold value F, the battery converter shifts from its first operating mode 1 in a second operating mode 3 in that it sets the output of electrical power from the battery and waits for availability of locally generated electrical power to recharge the battery above the threshold value F. If the SOC is up to below falls a second lower threshold D, as far as electrical power from the output side connected AC mains is available, the battery is charged with this electrical power up to a first upper threshold E, to continue for a long time without availability of locally generated electrical power, until the second lower threshold D is fallen below again. The area of the second operating mode 3 is here in three sections 2 . 6 and 30 divided. In the top part 2 above the first upper threshold E, the recharging of the battery takes place only with locally generated electrical power. Therefore, the difference between the first lower threshold F and the first upper threshold E is also referred to as "PV Res" for "photovoltaic reserve".

Between the first upper threshold value E and the second lower threshold value D, the second partial area extends 6 in that, coming from a SOC below the second lower threshold value D, the charging of the battery also takes place with electrical power from the AC network. A difference between the first upper threshold E and the second lower threshold E also referred to herein as Grid Res for Grid Reserve, English for grid reserve. Below the second lower threshold D, a subregion closes 30 the second operating mode 3 until electrical power from the battery is used in the event of AC mains failure to maintain backup power operation using the battery converter. In this case, a difference between the second lower threshold value D and the third lower threshold value C marks an available energy reserve for this backup power operation, here referred to as "backup" for backup reserve.

If the third lower threshold value C is also undershot from the SOC of the battery, the battery converter enters a fourth operating mode 20 over, in which electrical power is expended from the battery only for the standby consumption of the battery converter itself. In this way, the battery converter still comparatively long by, then, if at its output again electrical power to charge the battery is available to resume its full function immediately. A difference between the third threshold C and the next lower fourth lower threshold B is therefore also referred to as "battery res" for battery reserve. At an SOC below the fourth threshold B, the battery converter is turned off. That is, the operating mode 10 is "off". A difference between the fourth lower threshold B and a fifth lower threshold A at the SOC of 0% is also referred to herein as Prot Res for Protection Reserve; English for protection reserve, designated. This amount of energy ensures that the battery converter 11 when the AC mains has returned, at least manually restartable, which is possible down to the lower threshold A down. The Prot Res covers the self-discharge of the battery 14 even over longer periods of time, even if it represents only a few percent of the SOC.

When the battery 14 due to renewed electrical power at the output of the battery converter 11 can be recharged, there is a change between the operating conditions 10 . 20 . 3 and 1 in reverse order as before with decreasing SOC. In this case, upper threshold values at which the respective change takes place can each be somewhat higher than the lower threshold values B, C, D and F, so that there is no jumping back and forth between two adjacent operating modes. When electrical power from the AC mains 13 is available, from low SOC, the recharging of the battery up to the upper threshold E with electrical power, which also comes from the AC mains 13 can come, and only about it exclusively with locally generated electrical energy. In that regard, then here is the second mode of operation 3 between the subareas 6 and 3 divided.

4 illustrates another embodiment of the present invention, in which 3 the third lower threshold C and corresponding to the lying between this third lower threshold C and the overlying second threshold D subarea 30 the Bu Res, which for the backup power operation in the second operating mode 3 is held, deleted. Instead, down to the second lower threshold D directly is the area of the Bat Res with the second mode of operation 20 and next, when falling below the fourth lower threshold B, the battery converter enters the operating mode 10 "switched off. This sequence of the lower threshold values F, D and B is applicable if the battery converter does not have to provide any special energy reserve Bu Res for an emergency power operation in the event of a failure of the AC mains connected to the battery converter on the output side.

5 Figure 12 shows yet a sixth and seventh lower thresholds G and H, which are maximized on both sides of the self operating mode, in which self-consumption of locally generated electrical energy is maximized, energy reserves "Func Res" and "Sto Res" to provide positive control power and negative control power be maintained for the AC network. These functions, also referred to as network services, serve to stabilize the AC network, thereby transferring energy from the AC network into the battery, if more energy is added to the total AC power is fed as consumed, and vice versa, energy from the battery is supplied to the AC grid when the global consumption exceeds the feed. "Func Res" stands for "functional reserve" and "Sto Res" stands for "storage reserve", English for storage reserve. The sixth lower threshold G separates the area of the operating mode Self, here a fourth operating mode 4 is, although he according to the operating mode Self 1 from a range of the first operating mode directly above the first lower threshold F 1 from. In the operating mode 1 Here, no electric power is output from the battery more to increase the self-consumption of locally generated electrical power, but only to stabilize the output side connected to the battery converter power grid. In the area of Sto Res is a fifth mode of operation 5 of the battery converter 11 active, in which he feeds excess electrical power from the AC mains into the battery, but no more locally generated power. Rather, this locally generated power, if it is surplus, is reduced. From this fifth mode of operation 5 If the temperature falls below the seventh lower threshold H, the battery converter enters the fourth operating mode 4 above. When positive and negative balancing power with the battery converter 11 for the AC mains connected on the output side 13 is to be provided, the application of the additional sixth and seventh lower thresholds G and H makes sense. However, the additional sixth lower threshold value G can also be dispensed with if both positive and negative control power for the AC network is to be provided, in particular if the first upper threshold value E and the second lower threshold value D are relatively far below the first lower threshold value F, allowing the provision of positive control power in the second mode of operation 3 is not associated with the risk that shortly after the SOC of the battery falls below the second lower threshold D, so that the battery is charged from the AC mains out.

In 6 is in addition to 3 the time plotted in the direction of the abscissa. Specifically, a period of one year is shown here. Over this year, the first lower threshold F will be changed seasonally. In summer 7 it lies deeper and thus increases the range of the operating mode Self for self-consumption, because in the summer with the photovoltaic generator 18 locally generated electrical energy will be available again at short notice even after a decline. In the other seasons, the first lower threshold F rises to the winter, where it is comparatively close to a SOC of 100% and leaves only a subset "Min Self" for the optimization of self-consumption, which is given throughout the year.

7 illustrated in one 6 corresponding to a seasonal change not only of the first lower threshold value F, but also the second lower threshold value D and the intervening first upper threshold value E, the operating modes 1 and 3 to adapt the battery converter even more to the seasonal characteristics, until falling below the third threshold C, the battery converter must be switched to standby mode. As well in 6 as well as in 7 For example, the seasonal variation of the first lower threshold F and also the seasonal variation of the second lower threshold D and the first upper threshold E may correspond to a period of a cosine function of one year duration. In the northern hemisphere, this is around the calendar year and in the southern hemisphere by one year, which starts in the middle of winter, so that the threshold values D, E and F also assume their lowest values in summer.

The changes in operating modes described in connection with the preceding figures are in 8th in the form of a decision tree and in 9 in the form of a decision network. The decision tree is tackled at any time from the start.

In 9 is one of a line 8th enclosed area of the one in which the AC mains, which is connected to the battery converter on the output side, provides electrical power. Everything outside the line 8th corresponds to a power failure. In 9 "reg" and "no reg" indicate available locally generated electrical power or unavailable locally generated electrical power.

LIST OF REFERENCE NUMBERS

1

First operating mode

2

Part of the second operating mode

3

Second operating mode

4

Fourth mode of operation

5

Fifth operating mode

6

Part of the second operating mode

7

summer

8th

line

9

coordinating point

10

Operating mode "off"

11

battery converter

12

separation point

13

AC power

14

battery

15

load

16

islanding

17

inverter

18

photovoltaic generator

19

separation point

20

Third operating mode

21

Dc link

22

DC / AC converter

23

DC / DC converter

30

Part of the second operating mode

A

Fifth lower threshold

B

Fourth lower threshold

C

Third lower threshold

D

Second lower threshold

e

First upper threshold

F

First lower threshold

G

Sixth lower threshold

H

Seventh lower threshold

Claims (19)

Method for operating an AC network ( 13 ) connected bidirectional battery converter ( 11 ) taking into account the availability of locally generated electrical power, comprising: - defining several operating modes ( 1 . 3 . 4 . 5 . 10 . 20 ) of the battery converter ( 11 ) with regard to an input of electrical power into a battery connected on the input side ( 14 ) and outputting electric power from the battery ( 14 ) depending on a state of charge of the battery ( 14 ) and output electric power available; Defining several threshold values (A to G) for the state of charge of the battery ( 14 ); and - when falling below a first lower threshold (F), switching from a first operating mode ( 1 ), in which electrical power from the battery ( 14 ) is output when a local power requirement is not covered by the locally generated electrical power and / or when a global supply of electrical power in the AC power grid ( 13 ) and in the electrical power in the battery ( 14 ) is supplied when the locally generated electrical power exceeds the local power requirement and / or when a global oversupply of electrical power in the AC power grid ( 13 ), in a second operating mode ( 3 ), characterized in that - in the second operating mode ( 3 ) no electrical power from the battery ( 14 ) or only then electrical power from the battery ( 14 ) is output when the local power requirement is not met at all, and electrical power in the battery ( 14 ) is supplied when locally generated electrical power is available and / or when a global oversupply of electrical power in the AC power grid ( 13 ) is present, that in a state of charge (SOC) below a second lower threshold (D), which is below the first lower threshold (F), if electrical power is available on the output side, the battery ( 14 ) by charging electrical power until reaching a first upper threshold (E) that is less than or equal to the first lower threshold (F), a first difference (Grid Res) between the first upper threshold (E) and the first second lower threshold (D) is selected so that a standby consumption of the battery converter ( 11 ) is covered for a predetermined first period. Method according to claim 1, characterized in that during charging of the battery ( 14 ) until the first upper threshold (E) of the battery converters ( 11 ) is operated with an optimized efficiency. Method according to claim 1 or 2, wherein in the second operating mode ( 3 ) electrical power from the battery ( 14 ) is output when the local power requirement is not covered at all, characterized in that falls below a third lower threshold (C), which is below the second lower threshold (D), of the second operating mode ( 3 ) into a third operating mode ( 20 ), in which electrical power from the battery ( 14 ) only to cover a standby consumption of the battery converter ( 11 ) is used and electrical power in the battery ( 14 ) is fed in if electrical power is available on the output side. A method according to claim 3, characterized in that a second difference (Bu Res) between the second lower threshold value (D) and the third lower threshold value (C) a predetermined amount of energy for a backup power operation ( 30 ) in the second mode of operation ( 3 ) covers. A method according to claim 3 or 4, characterized in that when falling below a fourth lower threshold (B), which is below the third lower threshold (C), the battery converter ( 11 ) is switched off. Method according to claim 1 or 2, wherein in the second operating mode ( 3 ) no electrical power from the battery ( 14 ), characterized in that when falling below a fourth lower threshold (B), which is below the second lower threshold (D), the battery converter ( 11 ) is switched off. Method according to claim 5 or 6, characterized in that a third difference (Bat Res) between the lowest lower threshold value (C or D) lying above the fourth lower threshold value (B) and the fourth lower threshold value (B) represents the standby consumption of the Battery converter ( 11 ) for a predetermined second period of time. Method according to one of Claims 5 to 7, characterized in that a fourth difference (Prot Res) between the fourth lower threshold value (B) and a fifth lower threshold value (A), up to which at least manual restarting of the battery converter ( 11 ) is still possible, the self-discharge of the battery ( 14 ) for a predetermined third period. Method according to one of the preceding claims, characterized in that, when falling below a sixth lower threshold value (G), which lies above the first lower threshold value (F), from a fourth operating mode (FIG. 4 ), in which electrical power from the battery ( 14 ) is output when the local power requirement is not covered by locally generated electrical power and when there is a global under-supply of electrical power and in the electrical power in the battery ( 14 ) is supplied when the locally generated electrical power exceeds the local power requirement and when there is a global oversupply of electrical power, in the first operating mode ( 1 ), wherein in the first operating mode ( 1 ) electrical power from the battery ( 14 ) is output when there is a global shortage of electrical power and in the electrical power in the battery ( 14 ) is supplied when the locally generated electrical power exceeds the local power requirement and when there is a global oversupply of electrical power. A method according to claim 9, characterized in that a fifth difference (Func Res) between the sixth lower threshold (G) and the first lower threshold (F) provides a certain average positive control power for a predetermined fourth period of time. A method according to claim 9 or 10, characterized in that when falling below a seventh lower threshold (H), which is above the sixth lower threshold (G), of a fifth operating mode ( 5 ), in which electrical power from the battery ( 14 ) is output when a local power requirement is not covered by locally generated electrical power and / or when there is a global under-supply of electrical power, and in the electrical power into the battery ( 14 ) is fed into the fourth operating mode when there is a global oversupply of electrical power ( 4 ) is changed. A method according to claim 11, characterized in that a sixth difference (Sto Res) between a maximum charge of the battery (SOC 100%) and the seventh lower threshold (H) provides a certain average negative control power for a predetermined fifth time period. Method according to one of the preceding claims, characterized in that at least one threshold value (F, E, D) for summer ( 7 ) and after the summer ( 7 ) is raised again. Method according to Claim 13, characterized in that the annual profile of the at least one threshold value (D, E, F) resulting from the reduction is cosinusoidal. Method according to one of the preceding claims, characterized in that at least one threshold value (D, E, F) is determined depending on weather forecasts. Method according to one of the preceding claims, characterized in that at least one lower threshold value (B, C, F, G, H), when falling below it between two operating modes ( 20 . 10 ; 3 . 20 ; 1 . 3 ; 4 . 1 ; 5 . 4 ) is assigned an upper threshold value which is greater than or equal to the lower threshold value (B, C, F, G, H) and when it is exceeded in the reverse direction between the same operating modes ( 10 . 20 ; 20 . 3 ; 3 . 1 ; 1 . 4 ; 4 . 5 ) is changed. Battery converter ( 11 ) with measuring devices for detecting the state of charge (SOC) of a connected battery ( 14 ) and with a controller that carries out the method according to any one of the preceding claims. Battery converter ( 11 ) according to claim 17, characterized in that the controller determines all threshold values (A to H) on the basis of external inputs and / or own measured values. Battery converter ( 11 ) according to claim 17 or 18, characterized in that the battery converter ( 11 ) a DC / AC converter for direct connection to an AC mains ( 13 ) or one with an AC mains ( 13 ) connectable isolated grid ( 16 ) or a DC / DC converter for connection to an input-side DC voltage intermediate circuit ( 21 ) an output side to an AC network ( 13 ) connected DC / AC converter ( 22 ), wherein at least one further current source is connected in parallel with the battery converter ( 11 ) to the DC voltage intermediate circuit ( 21 ) is connectable.

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